Enhanced Ground Proximity Warning Systems (EGPWS), such as that produced by Honeywell, include look-ahead algorithms that were designed assuming all engines climb performance availability. This includes a minimum 6-degree climb gradient for the look-ahead threat algorithm. This number was chosen to represent the minimum all engines operating climb capability of modem air transport category aircraft. In addition, the recommended recovery procedure from a hard EGPWS Pull-up aural alert is a straight-ahead pitch up to best available climb angle.
This works well under normal operating conditions but not in case of an engine out condition on takeoff where the certified minimum climb gradient can be as low as 2.4%. To make matters worse some engine out procedures, especially in mountain valleys, require the aircraft to turn shortly after takeoff since with the degraded climb performance the aircraft cannot out climb the terrain ahead.
Therefore, during these engine out departures the current EGPWS may not provide the desired response. Due to the lower allowed terrain clearances and the close maneuvering to terrain EGPWS alerts may be given. EGPWS Caution alerts are still desirable but hard Pull-up alerts are a concern since in most cases the standard EGPWS recovery maneuver should NOT be performed since the aircraft may not be able to out climb the terrain. Pilot reaction to the alert may put the aircraft in a degraded climb performance situation. In other words, FAA aircraft certification requirements require aircraft manufacturers to design aircraft that can meet minimum climb-out restrictions even in an engine out situation. Therefore, deviating from flying the best engine out climb performance procedures can only increase the danger of impacting a departure obstacle (ground, radio tower). Instead, the pilot should stick to the prescribed engine out procedure.
In one system that tries to solve this problem, the system modifies the minimum 6-degree climb angle used for alert calculations. Unfortunately, in the case of the engine out condition decreasing the assumed climb angle will in most cases just increase the changes of getting a nuisance alarm.
What is needed then is both a method for detecting the loss of performance condition and changes to the EGPWS alerting algorithm.
Before we can modify the look-ahead algorithms, we must be able to detect the loss of an engine on takeoff. The prior system above required a signal from the aircraft to indicate when an engine failure had occurred as well as numerous stored aerodynamic parameters. Unfortunately, this results in complex aircraft interfacing problems as well as significant data gathering to obtain the proper parameters.
Therefore, there is a need to come up with a method that reduces the burden and cost for determining an engine failure condition.
The present invention includes a system; method and computer program product for reducing nuisance warnings during low performance takeoff conditions. The system includes a first component that determines aircraft current climb rate and potential climb rate based on aircraft vertical speed data and velocity information and a second component that adds the determined current climb rate and potential climb rate. The system also includes a third component that disables alerts, if the sum of the current climb rate and potential climb rate differ from a predetermined climb rate by a threshold amount and if the aircraft is supposed to be in a maximum thrust condition (e.g. takeoff, missed approach).
In accordance with further aspects of the invention, the predetermined climb rate is based on all engine maximum thrust operation.
In accordance with other aspects of the invention, the all engine maximum thrust operation is based on a drag component, a weight component, and an all engines at maximum thrust component.
As will be readily appreciated from the foregoing summary, the invention provides a system that uses previously generated values to assess engine operation and provide alerts according to engine operation status.